The use of a small on chip memory area and high processing speed are essential for very accurately expressing a numerical value in a computer. To satisfy such limitations, a floating point type in which the data are separated into an exponent part and a mantissa part has been used. Early in the 1960s, data computation of a floating point expression, in a computer, was carried out by developing a software library function. The implementation provided low speed and occupied a large memory area. These problems had been overcome in some extent by the development of hardware adapting achievements in VLSI technology. However, improvements in processing speed still has a limitation that is essentially due to a lack of the parallel processing function of conventional logic gates. Accordingly, a multiplier circuit using a floating point expression also has a limitation in improving processing speed. Also, as the number of bits becomes larger, the number of gates increases greatly. Thus, the larger area on a chip occupied by a multiplier circuit having an increased number of gates is not economic.